There is conventionally known a sensor (human sensor) for detecting the existence of a human body using an infrared sensor. The human sensor is used for an automatic light switch and the like.
If, however, such a human sensor is influenced by infrared radiation from surrounding heat sources such as a light emitter and electronic components, it may malfunction. As a method of reducing the influence of infrared radiation from a surrounding heat source, a partition for shutting off the infrared radiation from the heat source is arranged between the human sensor and the heat source.
However, in order to provide the partition, a sufficiently wide space is required between the human sensor and the heat source. In the case of a small-sized device or where there is a requirement of design, such a wide space may be hard to provide. In addition, the partition inevitably results in an increase in the number of parts required.